Copter-3.3 beta testing

Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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                • Developer


                  Very sorry to hear about the crash.  No fun at all.

                  Probably hard to think about it much at this point but regarding the hard landings, with the fix in Copter-3.3.2 it uses the "leash" while descending.  This means it will start slowing it's descent rate at some altitude above 10m so that when it reaches 10m it's descending at the LAND_SPEED.  Previously it would change it's target descent rate at 10m, now it begins slowing much higher than that if necessary.

                  • Randy,

                     Is there a general advice/guidance on tuning large copters with slow motors and large propellers. I have previously had to use really high PIDs, in the range of 3.34 .(U7 420KV quad on 4S)

                     The new U8 135Kv quad on 6S, was rather unstable on low PID and I will be testing increase P at 3 and test flying again.


                  • Hi Ya . yes i think your are right i should try 3.3.2.on that machine, as you say it should start to slow sooner before 10m .. this is the issue, it races to 10m then tries to slow by that time its nearly touching the ground ... instead of racing down to earth then start slowing down before it hits the 10m... Yes losing that big machine is a hard one .. i think i will stick to faster moving props .. busy building a Y6 on 275Kvs on 8s ....trying to do the whole, more volts less amps thing :) i might try 12s on one of the sole survivors of the bigger motors on the test bench. ..

              • Had a noticeable drop in power twice while in ALT mode in test flights today.

                Frimware.Version: 3.3.2rc2

                 I also have SF10/C connected in serial

                 Log attached

                PS a bit unrelated but: This was the first flight of a large quad with 29"x9.5 props, and it wasn't tuned. But it was sluggish and unstable enough that I wouldn't trust to put it in autotune. I think I need to ramp up significantly the rates test fly and then tune

                • bin log here

                  Tony: temperature must have been ~5C

                  2016-02-10 10-51-40.bin

                • biggest question i would ask. Was it cold outside.? 

    • Dang... I just looked for 5 minutes.. I don't see it either.. Just this .. I think it defaults to 10M but I know you used to be able to change that. Must be looking right at it!! 

      RTL loiter time (ArduCopter:RTL_LOIT_TIME)

      Time (in milliseconds) to loiter above home before beginning final descent

      • Range: 0 60000
      • Increment: 1000
      • Units: ms
  • Randy: today a strong wind, I flyed with 3.3.3 pos hold and nothing strange; I'm going to try more things next days.

    • Developer


      Great, thanks very much for testing!

  • Developer

    Re Pixracer, we've done a special build of Copter-3.3.3 and put it in place on so you should be able to load the Quad code from MP's Install Firmware screen (either the default or "beta firmwares" links should work).

    So for now only the quad code is available but we will put the hexa, tri and y6 versions in place tomorrow.

    Because I used my pixracer to work with my QC snapdragon (aka "snappy") we have not actually test flown this exact binary so please be careful and it would be good if the first couple people reported back that it seems ok (or not ok).

    Sorry for the delay!

    P.S. because this pixracer build was done manually, MP's install firmware screen may initially tell you it's installing Copter-3.3.2 (or Copter-3.3.3-rc2) but it will actually install Copter-3.3.3.  This slightly bit of misinformation will go away when we do the official Copter-3.3.3 release.

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